Section 8. The chief superintendent, district supervisors, district superintendents and other employees and authorized agents of the bureau of shade tree management and pest control may enter upon any land within the commonwealth, and any local superintendent appointed under section thirteen and his employees and authorized agents may enter upon any land within his city or town, in accordance with the provisions of this chapter, for the purpose of determining the existence, over-all area and degree of infestation or infection caused by the public nuisances named in section eleven, suppressing and controlling said public nuisances and affixing signs to and removing, or causing to be removed, trees and wood infected with the Dutch elm disease or used as a breeding place of the beetles which spread said disease.